Thermostatic switch



April 5, 1938.

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Patented Apr. 5, 1938 `'UNITED STATES PATENT OFFICE Application June 30, 1936, Serial No. 88,208 In Great Britain March 12, 1936 13 claims. (C1. 2045137) This invention relates to snap action mechanism for operating electric switches, valves and other devices and comprises an improvement in or modification of the invention described and 5 claimed in my co-pending application, filed 22nd October, 1935, No. 46,200.

The snap action mechanism setforth in the said co-pending patent application comprises a non-resilient operating member pivoted at one i end, a member acting resiliently on said operating member in such manner as to urge it towards but slightly offset from its pivot so as to exert a turning moment in one direction, and means for applying a resilient force at right angles to said operating member against the action of said member acting resiliently to exert a turning moment in the opposite direction, the arrangement being such that as the moment due to the resilient force increases it overbalances the opposing moment and causes movement of the said operating member to take place, the opposing moment decreasing much more rapidly than the applied moment whereby the snap action takes place before the operating member passes through dead centre or neutral position, such movement of the said operating member taking place at the end remote from its pivot point to operate an electric switch, valve or the like.

Further, in the constructions described in the above mentioned speciilcation, the operating member is pressed against the pivot point on the body of the device in which it is incorporated by a resilient force which is described as being supplied either by the resiliency of the strut member itself or by the resiliency of one or both of the supports or brackets on the body to which the strut member and the operating member are pivoted respectively.

According to the present invention, in snap action mechanism, as set forth in my said prior patent application, the resilient force is supplied by the operating member itself by making said member resilient betweenits two pivotal points.

The invention will now be described by way of example with reference to the accompanying drawing, in which:-

Figures 1 and 2 are sectional elevations of one form of the invention.

Figure 3 is a sectional elevation of a modifica-v tion oi.' Figure 1.

Figures 4, 5 and 6 show an alternative form of making the operating member resilient.

Figure 7 shows a thermostatic switch in sec tion, and

Figure 8 is a side view of Figure 7.

In carrying the invention into effect according to the form illustrated in the figures of the accompanying drawing and as applied by way of example to the thermostat having a short-gap large contact switch, as set forth inthe specication of my co-pending application filed 22nd October, 1935, No. 46,200, a body I is mounted on the casing 2, but insulated therefrom by material I3, and is provided with an upstanding support 3 on one face of which a horizontal V groove 4 is provided, and in this V groove is located an operating member 5 which lies substantially parallel to said body,r the operating member having a knife edge 6 atone end parallel to said body about which it pivots in the V groove 4. 'I'he length of the groove is approximately equal to the width of the operating member 5 so as toy prevent it from moving sideways.

The other end of the operating member is provided with a contact 'l which engages with a fixed contact 8 mounted upon a suitable member 9 secured to the body I by means of pillars I0, but insulated therefrom by suitable insulating means. This limits the movement in one direction. The contact 8 is preferably made adjustable in the member 9 and when set in the correct position is locked therein by the lock nut II. An adjustable stop I2, or the like, is provided upon the body I so as to limit the movement in the other direction and thus control the opening or gap between the contacts to any suitable amount. If desired, the stop I2 may be mounted upon the operating member.

Provided upon the said body on the opposite end to the support 3 is another support I4 in which is situated a suitable screw or the like I5 having a cup or conical bearing I6 which may be jewelled if desired, or made of hardened steel or other suitable material. The operating member 5 is drilled longitudinally slightly offset of said knife edge 6 and the bottom of the hole is provided with a similar cup or conical bearing I1 which may be hardened steel or other material and pressed into position. A rigid strut member I8 is provided with conical pivot points, and this is iitted so that one end rests in the bearing Il within the pivoted member and the other end in the bearing I6 in the support. The screw I5 is then tightened up so that the strut member I8 keeps the operating member 5 in the V groove, and due to its pressure being oifset tends to turn the operating member about its knife edge and press the two contacts together. Also supported uponthe pillars I0 or the like is a spring member 20 having a depending tongue 2| or the like,

which is arranged so that it will make contact with the operating member 5.

The thermally sensitive member comprises a brass tube 25 securely fixed at one end to the casing 2 and at the other end to a rod 26 which is a sliding iit in said easing. The rod 26 is connected rigidly to a stirrup member 21 which is provided with an adjusting screw 28 having a pointed end or tip 29 made of insulating material such, for example, as glass or porcelain. This tip 29 is arranged to press against the spring member 20 so that its depending tongue 2l will press against the operating member 5 and thus apply a lateral force thereto. which will overbalance the longitudinal pressure and flick over the operating member 5 so that the contacts ily apart. The spring member is arranged to magnify the movement of the means which applies the lateral force to the strut member. A knurled head 3i, having a pointer thereon, is provided upon the adjusting screw 28 so as tol adjust the temperature at which the contacts open. A suitable scale or the like 32 is provided upon the top of the cover 33 which fits on to the casing 2 and encloses the instrument.

According to the present invention the necessary energy to carry over the contact 'l with a snap action is stored in the operatingl member 5 by providing it with a transverse slit or saw cut A between the pivotal points 6 and i1 such that the section of the operating member is so reduced by said slit or saw 4cut that the necessary spring or resiliency is given thereto. It is found in practice, that a small amount of resiliency is all that is required to cause the snap action to take place and therefore the depth of the slit or saw cut A into the section of the metal of which the operating member is made will depend upon the resiliency of the metal itself to give the required spring. The bottom extremity of the slit or saw cut may be terminated by a small circular hole B which may be drilled first in the operating member and then the slit or saw cut made so that it enters the circular hole.

According to a modification illustrated in Figure 3, the section of the operating member may be reduced to give the necessary resilience or spring by cutting out a portion O of the member such that a thin or narrow strip is left on each side connecting the two portions of the member together and this will result in the necessary spring being provided. This may be done by drilling a hole transversely through the member. The cut out portion O may be any other shape than circular.

Further, instead of making the actual spring by means of the resiliency of the material itself, the operating member between the two pivotal points may be made telescopic, as shown in Figures 4 and 5, and the two portions 5 and 51 pressed away from oneanother by a compression spring S. In this manner', when the member is pressed by the strut member up against the pivotal point of the bracket, the spring will give the necessary resilience to the force.

If desired, instead of makingthe whole of the operating member between the two pivotal points as two separate pieces 5 and 51 which telescope one within the other, the actual cup bearing I1 may be made separate and a slidable fit into the operating member 5 and at the back of this a compression spring S may be fitted. In this manner, the necessary resilience, when the strut member I8 supplies a force to the cup bearing, is obtained through the compression spring, and

the operating member itself will, in this case, supply the necessary resiliency.

It is to be understood that various other methods of making the operating member resilient just between its pivotal points can be devised, but the portion-of the operating member on which the contact, valve or the like is mounted, must be kept rigid so as to prevent any loss to, or unnecessary motion of the operating member to take place before the contacts move away from one another with the snap action.

I claim:

1. A snap action make and break mechanism comprising in combination a body. an operating member pivoted at one end to said body. means to make the said operating member resilient at a point between its two extremities, a member at the other end of said body, with which the other end of said operating member makes contact, a member pivotally supported at one end on said body and at the other end on said operating member applying a resilient turning moment to said operating member in one direction, and a resilient member mounted upon said body adapted to apply a force which creates a turning moment which is applied in the opposite direction to said operating member, movement of said operating member taking place when one turning moment overbalances the other turning moment, and the snap action being due to the overbalanced turning moment decreasing more rapidly than the other turning moment and taking place before the said operating member reaches the dead centre or neutral position.

2. A snap action make and break short gap mechanism, comprising in combination a body. two upstanding supports on said body, an operating member pivotally supported at one end on one of said supports, means to make the said operating member resilient at a point between its two extremities, a floating member pivotally supported upon said operating member and said other support applying a resilient turning moment in one direction, a member on said body, a. member on said operating member contacting with said body member, a resilient member mounted upon said body adapted to apply a force which creates a turning moment which is applied in the opposite direction to said operating member, and means coacting with said resilient member to apply pressure thereto, said snap action taking place before the said operating member reaches the dead centre or neutral position.

3. A snap action make and break mechanism comprising in combination a body, a resilient operating member pivoted at one end to said body, a reduction of sectional area at a point on said' operating member, a member at the other end of said body, with which the other end of said operating member makes contact, a member pivotally supported at one end on said body and at the other end on said operating member applying a resilient turning moment to said operating member in one direction, and a resilient member mounted upon said body adapted to apply a force which creates a turning moment which is applied in the opposite direction to said operating member, movement of said operating member taking place when one turning moment overbalances the other turning moment, and the snap action being due to the overbalanced turning moment decreasing more rapidly than the other turning moment and taking place before the said operating member reaches the dead centre or neutral position.

4. A snap action make and break short gap mechanism, comprising in combination, a body, two upstandlng supports on said body, a resilient operating member pivotally supported at one end on one of said supports, a reduction of sectional area at a point on said operating member, a floating member pivotally supported upon said operating member and said other support applying a resilient turning moment in one direction, a member on said body, a member on said operating member contacting with said body member, a resilient member mounted upon said body adapted to apply a force which creates a turning moment which is applied in the opposite direction to said operating member, and means coacting with said resilient member to apply pressure thereto, said snap action taking place before the said operating member reaches the dead centre or neutral position.

5. A snap action make and break mechanism comprising in combination a body, a resilient operating member pivoted at one end to said body, and formed of two portions telescoping together, spring means pressing said two portions -away `from one another, a member at the other end of said body, with which the other end of said operating member makes contact, a member pivotally supported at one end on said body and at the other end on said operating member applying a resilient turning moment to said operating member in one direction and a resilient member mounted upon said body adapted to apply a force which creates a turning moment which is applied in the opposite direction to said operating member, movement of said operating member taking place when one turning moment overbalances the other turning moment and the snap action being due to the overbalanced turning moment decreasing more rapidly than the other turning moment and taking place before the said operating member reaches the dead centre or neutral position.

'6. A snap action make and break short gap mechanism, comprising in combination, a body, two upstandlng supports on said body, a resilient operating member pivotally supported at one end on one of said supports, and formed of two portions telescoping together, spring means pressing said two portions away from one another, a oating member pivotally supported upon said operating member and said other support applying a resilient turning moment in one direction, a member on said body, a member on said operating member contacting with said body member, a resilient member mounted upon said body adapted to apply a force which creates a turning moment which is applied in the opposite direction to said operating member, and means coacting with said resilient member to apply pressure thereto, said snap action taking place before the said operating member reaches the dead centre or neutral position.

7. A snap action make and break short gap thermostatic switch comprising in combination a body, an operating member pivoted at one end to said body, means to make the said operating member resilient at a point between its two extremities, a member at the other end of said body, with which the other end of said operating member makes contact, a member pivotally supported at one end on said body and at the other end on said operating member applying a resilient turning moment to said operating member in one direction, and a resilient member mounted upon said body adapted to apply a force which crean operating member pivotally supported at one end on one of said supports, means to make the said operating member resilient at a point between its two extremities, a floating member pivotally supported upon said operating member and said other support applying a resilient turning moment in one direction, a member o'n said body, a member on said operating member contacting with said body member, a resilient member mounted upon said body adapted to apply a forcel which creates a turning moment which is applied in the opposite direction to said operating member, and means coacting with said resilient member to apply pressure thereto, said snap action taking place before the said operating member reaches the dead centre or neutral position.

9. A snap action make and break short gap thermostatic switch comprising in combination a body, a resilient operating member pivoted at one end to said body, a reduction of sectional area at a point on said operating member, a member at the other end of said body, with which the other end of said operating member makes contact, a member pivotally supported at one end on said body and at the other end on said operating memberapplylng a resilient turning moment to said operating member in one direction, and a resilient member mounted upon said body adapted to apply a force which creates a turning moment which is applied in the opposite direction to said operating member, movement of said operating member taking place when one turning moment overbalances the other turning moment, and the snap action being due to the overbalanced turning moment decreasing more rapidly than the other turning moment and taking place before the said operating member reaches the dead centre or neutral position.

l0. A snap action make and break short gap thermostatic switch comprising in combination,

a body, two upstanding supports on said body,-

a resilient operating member pivotally supported at one end on one of said supports, a reduction of sectional area at a point on said operating memberpa floating member pivotally supported upon said operating member and said other support applying a resilient turning moment in one direction, a member on said body, a member on said operating member contacting with said body member, a resilient member mounted upon said body adapted to apply a force which creates a turning moment which is applied in the opposite direction to said operating member, and means coacting with said resilient member' to apply pressure thereto, said snap action taking place before the said operating member reaches the dead centre or neutral position.

11. A snap action make and break short gap thermostatic switch comprising in combination, a body, two upstandlng supports on said body, a resilient operating member pivotally supported at one end on one of said supports, a oating member pivotally supported upon said operating member and said other support applying a resilient turning moment in one direction, a con tact on said body, a contact on said operating member engaging with said body contact, means for preventing, said operating member passing through dead centre or neutral position when the contacts are opened, a resilient member mounted upon said body and pressing upon said operating member applying a turning moment in the opposite direction, and a thermally sensitive member ooacting vwith. said resilient member to apply pressure thereto.

l2. A snap action make and break short gap switch comprising in combination a body, two upstanding supports on said body, a resilient operating member pivotally supported at one end on one of said supports, a floating member pivotally supported upon said operating member and said other support applying a resilient turning moment in one direction to said operating member, means for adjusting the end pressure fon said floating member, a contact on said body, a conm tact on said operating member engaging with said body contact, means for preventing said operating member passing through dead centre or neutral position when the contacts are opened, a resilient member mounted upon said body and pressing upon said operating member applying a turning moment in the opposite direction, and

means coacting with said resilient member to apply pressure thereto.

13. A snap action make and break short gap switch comprising in combination, a body, two upstanding supports on said body, a V groove in one support, a cup shaped bearing in the other said support, a resilient operating member, a knife edge on said operating member engaging said V groove on said support, a cup shaped bearing on said operating member, a floating member supported in said cup bearings on the support and operating member respectively, said floating member applying a resilient turning moment in one direction to said operatng member, means for adjusting the force exerted by said floating member upon said operating member, a contact on a portion o! said operating member remote from the two bearings, a contact on said body adapted to be engaged by said contact on said operating member, a stop to limit the gap i between the contacts and to prevent the operating member from passing through dead centre or neutral position, a resilient member mounted upon said body to press upon said operating member for applying a turning moment in the opposite direction, and means coacting with said resilient member to apply pressure thereto.

THOMAS GUTHRIG RICHMOND. 

